This invention relates to semiconductor devices of the Hall effect type, to methods of fabricating such devices, and to applications thereof.
As is well known, a Hall effect device comprises a plate-like body of a semiconductor material through which a transverse magnetic field may be applied. The effect of the magnetic field is to deflect an electric current flowing across the body between a pair of current electrodes, this deflection of the current inducing a potential difference between a pair of sensor or Hall electrodes disposed one on each side of a line joining the two current electrodes. The magnitude of this Hall voltage V.sub.H is given approximately by the expression EQU V.sub.H =BI/nde
where B is the applied magnetic field intensity; I is the current through the device; n is the carrier concentration of the device material; e is the electronic charge and d is the device thickness. Thus, the output Hall voltage is inversely proportional to the device thickness and is directly porportional to the current, which in turn is a function of the carrier mobility in the semiconductor material.
Hall effect devices are used in a variety of applications, their most important features being the complete absence of moving parts and the provision of a high degree of isolation between the control input and the device output. These features have made the use of such devices in e.g. telephone switching applications an attractive proposition. The use of Hall effect devices is however limited at present by their relatively low sensitivity which in turn results in a relatively high power consumption.
From the expression given above, it will be seen that the sensitivity of a Hall effect device can be enhanced by using a semiconductor material having a relatively high carrier mobility, e.g. gallium arsenide, and at the same time reducing the device thickness to a minimum. However, previous attempts to produce thin wafers of gallium arsenide have not been successful.
U.S. Pat. Nos. 3,265,959; 3,943,481 and 4,021,767 relate to Hall-effect devices.